The present invention relates to a method for forming an image, and more particularly to a method for forming an image by heat development.
A photographic method using silver halide has been most widely used because this method results in excellent in photographic characteristics such as sensitivity and gradation control as compared with other photographic methods, such as an electrophotographic method and a diazo photographic method. In recent years, a technique permitting easy and rapid formation of images in the image-forming processing of light-sensitive materials using silver halide has been developed in which dry processing, such as heating, is employed in place of wet processing, such as a processing using a developer.
Photographic materials to be processed by the above image-forming method including a combination of heat developable color light-sensitive element comprising light-sensitive silver halide and a dye providing substance forming or releasing a hydrophilic diffusible dye, and a dye-fixing element to transfer and fix therein the diffusible dye in the presence of a small amount of water, as described in Japanese Patent Application (OPI) Nos. 58432/83 and 218443/84 (the term "OPI" as used herein means a "published unexamined patent application").
During dry processing by the above heat development method, water is supplied in a constant amount not more than the absorption amount of the coating at the time of maximum swelling as described in Japanese Patent Application (OPI) No. 238056/86. Therefore, certain advantages result such as a reduction in the mechanical strength of the coating due to the softening treatment of the coating which is carried out in order to facilitate the permeation of a developer in a conventional wet processing step; and a shrinkage of the coating (reticulation) at the drying step after processing do not occur.
In the heat development dry processing, however, it is necessary that the processing be carried out in the presence of a small amount of water. Since photographic performance varies with the amount of water supplied, a constant performance in terms of photographic characteristics cannot be obtained unless the amount of water supplied is made constant.
Another problem occurring in these types of conventional systems is that when a light-sensitive element is peeled apart from a dye-fixing element after the development and dye diffusion transfer in the presence of a constant amount of water, either all or a part of the coating of the light-sensitive element is bonded together with the coating of the dye-fixing element and cannot be peeled apart with ease. Furthermore, if the light-sensitive element is forcibly peeled apart from the dye-fixing element, the coating is peeled apart, causing damage or contamination of the peeled surface and thus no satisfactorily sharp image can be obtained.
Still another problem is that when the dye-fixing element is used in heat development after being stored under low humidity conditions, "white dots" (transfer unevenness, i.e., localized missing of transferred dye) is observed in the image.
A technique to obtain an image having an improved S/N ratio by increasing the effective activity of development and transfer has been desired.